to discard as useless or unsatisfactory: The mind rejects painful memories.

to cast out or eject; vomit.

to cast out or off.

Medicine/Medical. (of a human or other animal) to have an immunological reaction against (a transplanted organ or grafted tissue): If tissue types are not matched properly, a patient undergoing a transplant will reject the graft.

reject

n.

1550s, "a castaway" (rare), from reject (v.). Modern use probably a re-formation of the same word: "thing cast aside as unsatisfactory" (1893); "person considered low-quality and worthless" (1925, from use in militaries).